In most jurisdictions the charge of "stalking" is a very difficult to prove.
Violation of protective orders are pretty easy to gather evidence on and to prove.
Additionally, as your friend is discovering, it is very difficult to 'disappear' from the world in this day-and-age of technology.
Depending on how deeply you wish to get involved, you can establish phone service for her in your name and then the ex will have more trouble calling her. Let the police do the law enforcement work and support your friend in other ways.
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety."
Benjamin Franklin, 1755
"Living in our society is like living in a very tall building. The rich live on the top floors. The poor live on the lowest floors. And only the cops travel to all the floors. Only the cops see it all."
Det. Ted O'Conner - Chicago P.D